Radio frequency antennas-



Jan. 7, 1958 R. s. WEISS 24,413

RADIO FREQUENCY ANTENNAS- Original Filed Sept. 12, 1955' I 4Sheets-Sheet 1 INVENTOR Robert 8.7V'eiss f ATTORNEYS Fig.5 By

Jan. 7, 1958 R. s. WEISS RADIO FREQUENCY ANTENNAS Originai Filed Sept.12, 1955 4 Sheets-Sheet 2 ATTORNEYS INVENTOR Robert S- VVeiss Jan. 7,1958 R. s. WEISS RADIO FREQUENCY ANTENNAS Original Filed Sept. 12, 19554 Sheets-Sheet; 3

INVENTOR Robert S. Weiss ATTORNEYS Jan. 7, 1958 R. s. WEISS mm FREQUENCYANTENNAS Original Filed se i. 12, 1955 4 Sheets-Sheet 4 FREQUENCY C'vmc)LOW BAND 0 l m J. m w w E w 7-.T-

7 IO 6 0 w 2 r: i W 0 i w B w .2 J B u v m H w Pill El W5 ,6 W w A m f7Y .B w 2 United States Patent Ofiice RADIO FREQUENCY ANTENNAS Robert S.Weiss, South Euclid, Ohio, assignor to Finney Manufacturing Company,Cuyahoga County, Ohio, a corporation of Ohio Original No. 2,726,390,dated December 6, 1955, Serial No. 533,851, September 12, 1955.Application for reissue June 24, 1957, Serial No. 672,532

25 Claims. (Cl. 343-803) Matter enclosed in heavy brackets 1 appears inthe original patent but forms no part of this reissue specification;matter printed in italics indicates the additions made by reissue.

This invention relates to radio frequency antennas and particularly toantennas for television reception.

One of the principal problems facing the television antenna industry hasbeen to provide an antenna having high gain with a reasonably uniformimpedance over the entire low and high band frequency ranges establishedfor commercial television broadcasting. Another problem facing thisindustry has been to provide such an antenna which also has highdirectivity, w receptivity at other frequencies and a high front to backratio" to keep interference to a minimum. Still another problem has beento provide an antenna having all of the foregoing electricalcharacteristics and which is sufliciently small in size, light inweight, and easy to package. Ship, and install to be a practicalcommercial article. These problems are all so well recognized in the artas to require no elaboration.

Meeting all of the foregoing problems in an entirely satisfactory mannerfor all television channels in both the low and high band ranges issomething no one has even closely approached with any commerciallysuccessful product. All of the so-called broad band television antennason the market today involve many compromises in design. The best ofthese maintain close to their maximum efliciency over only a portion ofthe low and high television bands and most of them are substantiallyless eflicient in one band than in the other.

In the course of the development of this art, a few basic types ofdriven elements, or driven arrays of elements, have become generallyrecognized as being the most efiicient within the permissible sizelimitations imposed on any commercial antenna for this purpose. Ingeneral, those elements or arrays most suitable for low band operationare relatively inferior for high band operation, and vice versa. As aresult, most of the attention of the television antenna industry hasbeen directed to various modifications of these few basic types ofdriven elements to broaden their response, and to the utilization of oneor more of these few basic types of driven elements or driven arrays invarious combinations, with various arrangements of non-driven orparasitic directors and reflectors being employed in conjunctiontherewith to improve the gain over a broader frequency range.

In addition, to further increase the gain obtainable, the combinationsof driven and non-driven elements .or arrays have been duplicated byvertically stacking a number of such combination units on a single mast.The combination of stacked units is then connected to a singletransmission line by means of a suitably designed circuit for matchingthe impedance of the entire antenna to the impedance of the standard 300ohm transmission line.

Where improvement in any of these basic elements per se has beenaccomplished, this has generally involved the use of conductors ofimpractically large surface area to provide very low Q elements, or hasinvolved other undesirable features from the standpoint of weight, windresistance, production and material costs, etc. Where. combinations ofsuch basic elements have been utilized to obtain better performance,they have generally been quite complex, both electrically andstructurally. This has created manufacturing, packaging, shipping, andinstallation problems, which have often limited the commercialfeasibility of otherwise acceptable antenna designs.

The principal object of the present invention is to improve certain ofthe basic types of driven elements so as to render them more eflicientin meeting the above problems encountered in designing antennas for goodre= ception over long distances throughout both the low and highcommercial television bands.

Another principal object of the invention is to improve certain of thebasic types of driven elements in meeting the above problems whileemploying conductor materials of moderate cross-sectional dimensions, i,e. moderate or high Q elements, or elements having a high ratio oflength to surface area or diameter.

Another object of the invention is to achieve tore.- suiug je iv in anel tri ly nd structurally simple manner, to facilitate the stacking of aplurality of the modified units without undue structural omplication orthe necessity for using any complicated impedance mambing circuit.

Still another object of the invention is to provide a i p basic an nrray that i eilicient i both th low an h g n el vision fr quency rang s,th t dis crimina e w ll gains s na s at frequen ies outsid thes be fo ndu ef l in the solution of a wide varie y of Sp cialproblems in radio aswell televisi n- .A more specific objec of th inven n i t increase heeflicien y of a simple, basic antenna element, d signed for a relativelylow fwquency range, when it is used in a substantially higher freq encyrange.

Another specific object of he inven ion is to Prov de an arrangement foradjusting the impedance of a dipole antenna element more closely anduniformly to a desired value in two widely separated frequency ranges,,as the low and high band television fr q n y ranges,

Furt er obje ts of he inven ion are to ac omplish a l of the foregoingobjectives with an antenna structure eadily ad p a l to ting manufa inpackagin shipping, and installation facilities.

Where reference has been made in the foregoing dis cussion to a drivenantenna element, it is to be under.- stood that this has reference tothe manner in which that element would function if the antenna wereemployed for transmitting a signal instead of receiving a signal.Throughout this application, the term drivenis used in that sense, itbeing understood that the operation when transmitting signals is merelythe reverse of its operation when receiving signals.

Since conventional conductors used as the driven elemen-ts cf poleantennas are generally in h term of round tubes or rods where moderateand high Q values are acceptable, and sincethe .Q value of such dipoleelements ar e y with diameter, it is con enien to refer to the ratio .oflength to diameter, or to the L/D ratio, where L is the total tipeto tiplength of the dipole. This practice is followed hereinafter, it beingunderstood that reference to conductors haying specified L/D ratios areintended .to include conductors which are not round, but which have thsa Q alu and, therefore. n equivalent L/ D ratio.

3S. Hatent No- 2,:58-t),7'98 to Kolster discloses two or more low Qdipoles of substantially different length disposed in closely spacedparallel relationship, the dipoles being capacitatively coupled so thattheir net reactance, as seen by the associated transmission line, is lowat all frequencies throughout a wide band of frequencies, e. g.throughout a range in which the ratio of the terminal frequencies is 3:1or more. In this manner, Kolster obtamed a good impedance match to thesame transmission line and a low standing wave ratio over an entirefrequency range of that magnitude, with a very acceptable impedancematch and standing wave ratio over an even broader range. Kolsterdisclosed his results as being dependent upon the use of low Q elements,e. g. of the order of 5 and preferably much less. This involves the useof conductors of such large surface area as to be commercially andpractically of little value, for the reasons mentioned above,particularly where low cost, mass production and outdoor installationsare desired. In addition, though Kolsters antenna designs haveexcellent.

characteristics throughout a frequency range great enough to includeboth the low and high television bands, they possess the disadvantagefor television of having equally good, if not even better,characteristics over the frequency range between the low and high bands,and quite" good'characteristics above and below those bands. Asa

result, such antennas are incapable of efiiciently rejecting radiationoutside the desired low and high bands, with resultant interference fromunwanted radio frequency signals (police, amateur, radio-telephone, andother radio communication signals) and from radiation from industrialequipment and the like.

I have now found that, for efiicient operation over the low and hightelevision bands, the low Q elements of Kolster are unnecessary andundesirable, and that similar results can be obtained in those frequencyranges without a high capacitive coupling between conductors of largesurface area, which Kolster apparently considered essential. At the sametime, I have found that, by using moderate or high Q radiating elementsand omitting the added inductance preferably connected by Kolster acrossthe terminals of his antennas, the characteristics sought by Kolster canbe obtained in and substantially confined to the low and high televisionfrequency ranges, thus reducing the likelihood of interference fromunwanted signals. The present invention utilizes these discoveries toaccomplish the above recited objectives in a manner highly suited to theneeds of the television antenna industry, as hereinafter described indetail.

The invention is characterized by the modification of a conventionaldriven dipole, of either the straight or folded dipole type, constructedof moderate or [low] high Q conductors having an L/D ratio of at least40, and preferably higher, and having lengths selected for conventionaloperation in a low frequency range, such as the low band of commercialtelevision frequencies (54 to 88 mc.). As is well known, such an antennaelement, designed for low band operation, generally has a poor radiationpattern and relatively low gain when operating in the high band oftelevision frequencies (174 to 216 mc.).

The modification of a dipole, in accordance with the present invention,involves the mounting of one or more additional shorter dipole elements(which may have a similarly high L/D ratio) parallel to the first dipoleand in closely spaced relationship therewith, at least one preferablybeing disposed in front of the first dipole with respect to a signal tobe received.

The first dipole is driven in a conventional manner by connection to atelevision receiver through a two-conductor transmission line, but theadditional dipole or dipoles are non-driven. The spacing between thedriven dipole and the additional dipole or dipoles is substantially lessthan the spacing heretofore used between a driven dipole and a directoror reflector, so far as I am aware. This spacing is in the range ofabout 1% to about 7% or less of a half-wave length in the low frequencyrange to which the driven dipole is resonant, depending upon variousother factors hereinafter mentioned. The resultant mode of operation, ashereinafter explained, is radically different from the operation of adirector and/or a reflector in combination with a driven element.

In one simple form of the invention particularly suited for televisionreception, the driven dipole is preferably of the folded dipole typeadapted for use broadside to the signal'to be received. A singleadditional non-driven dipole is disposed parallel thereto and iscentrally aligned therewith in the path of the signal to be received, i.e. a straight line from the signal. source would pass through the centerof both the driven and non-driven dipoles.

The first or driven dipole is preferably made resonant as a half-wavedipole to a frequency near the center of the low band at, say, 65 me.The second or non-driven dipole is preferably approximately. one-thirdthe length.

of the first, so that it would then be resonant as a halfwave dipole at,say, me. near the center of the high band. In this case, the seconddipole would be longitudinally coextensive with approximately thecentral onethird of the first dipole.

The first or driven dipole of such an antenna, when dimensioned as ahalf-wave dipole in the low band range, is not materially affected bythe presence of thesecond dipole when operating in the low band range.The antenna, at the terminals of the first dipole, has very close to itsnormal impedance at its resonant frequency. As a result, it functionsessentially as a conventional half-wave.

folded dipole over the low band range as regards gain, impedance, andradiation pattern. However, when the antenna is operating in the highband range, I have discovered that the presence of the second dipole inclose proximity to the first, when properly dimensioned and positionedin front of the driven dipole, causes the antenna to have gain andimpedance characteristics and a radiation pattern in the two forwardquadrants that are closely similar to those of an array of three, highband, halfwave elements connected for in-phase operation as a collineararray. In addition, the combination has a substan tial front-to-b ackratio.

An array of three half-wave collinear elements, dimensioned for aboutthe center of the high band, has been widely recognized and accepted asbeing about the most eflicient array for television reception over thehigh band range. It has high gain, a narrow radiation pattern, and animpedance of about 300 ohms at its reactant frequency. Also, theimpedance variation over the high band range of frequencies is wellwithin the limits for eflicient transfer of energy to a 300 ohmtransmission line. Its principal drawback has been that it is arelatively inefiicient array when operating in the low band, far belowthe high band resonant frequency.

A half-wave folded dipole, dimensioned for about the center of the lowband, on the other hand, has been widely recognized as being about themost efficient, driven, halfwave element for television reception overthe low band range. It also has an impedance of about 300 ohms at itsresonant frequency, with relatively small impedance variation over thelow band range of frequencies. Its principal and well known drawback isthat it is a relatively inefficient array when operating in the highband.

By utilizing the discovery described above, the highly efficient anddesirable electrical characteristics of a collinear array on high bandand of a folded dipole on low band can be combined in one simple arraywith no complicated phasing stubs or impedance matching circuits whileutilizing conventional, moderate or high Q conductors. Thus, whenapplying my discovery to television reception over both the low and highband ranges, I preferably use a low band, half-wave, folded dipole asthe driven element to obtain a good impedance match to a 300 ohm lineover the low band range; and I dispose a folded dipole and in closeproximity thereto to produce .5 high gain in the high band range with agood impedance match to a 300 ohm line and high directivity.

At the resonant frequency of the half-wave folded dipole in the lowband, the impedance is very close to 300 ohms, and at some frequency inthe high band, depending upon the exact length and shape of thenon-driven element and its spacing from the folded dipole, the impedancecan also be brought very close to 300 ohms. To achieve optimum results,the precise length and shape of the non-driven element and its properspacing from the driven, folded dipole are best determinedexperimentally. However, when using a non-driven element about onethirdthe length of the driven dipole, the proper spacing will generally bewithin the range of about 1% to about 7% of a half-wave length at thelow band resonant frequency of the driven element. The size and shape ofthe added non-driven element is subject to considerable variation tosuit the particular needs, as hereinafter explained in more detail.

The same beneficial results may be Obtained with the non-driven dipoledisposed vertically above or below the driven dipole, instead of infront of the driven dipole, or with a pair of identical, transverselyaligned, non-driven dipoles, one disposed in front of and one behind thedriven dipole, with equal spacing except that, 'as would be expected inthese cases, the array has no front-to-baek ratio. Also, three or moresuch non-driven dipoles may be disposed in transversely alignedrelationship about the driven dipole in a generally cylindrical array.The use of a plurality of such transversely aligned, non-driven dipolesprovides greater impedance adjustably at the sacrifice of thefront-to-back ratio, but otherwise produces essentially the same resultsas when but one non-driven dipole is disposed in front of or above thedriven dipole.

Because the radiation of a given driven element may generally beconsidered to be constant for a given power input (assuming no change inimpedance match with the transmission line it is apparent that theaddition. Of a parasitic element or combination of parasitic elementsfor changing the radiation pattern, so as to, concentrate the radiationin a desired direction, essentially involves only a redistribution ofthe radiated energy without increasing its amount. Thus, narrowing orsharpening forward and rearward lobes and reducing or eliminating sidelobes in a radiation pattern increases the amount of the constant, totalenergy that is radiated in the forward and rearward directions without,however, increa ing the total energy radiated. This is the effect ofusing a pair of non-driven, parasitic dipoles closely spaced in frontand behind a driven dipole in the manner mentioned in the precedingparagraph. Similarly, where the same general change is made in theradiation pattern while also increasing the magnitude of the forwardlobe relative to the rearward lobe, 4 still greater proportion of thetotal energy is radiated in the forward direction as is normally desiredfor television reception, for example, and a smaller proportion of it isradiated in the rearward direction This is the efiect where only asingle, parasitic, non-driven dipole is employed in closely spacedrelationship with a driven db pole and in front of it or in theso-called position, Obviously, therefore, dispensing with a rearward,closely spaced, nonadriven dipole not only reduces the undesiredrearward radiation component with a resultant decrease in interferencefrom the rear when the antenna is used as a receiving antenna, but italso increases the forward radiation component so as to further increasethe gain in the desired forward or 0 direction. The improvedperformance, moreover, is achieved in this manner with a simpler,lighter weight, and less expensive array with consequent obviouscommercial advantages.

Where it is desired to use a longer driven dipole that is a full Wavelong or 3/2 waves long etc. at a frequency in the low band range, aplurality of longitudinally spaced, non-driven dipoles, or generallycylindrical arrays of o -d i en po s, may b si il r y associated withthe driven dipole to obtain the desired current phasing; end impedancevalues in the high frequency range in the non-driven dipoles areresonant In this case, the non-driven dipoles are still cut to operateas half wave elements in'the high frequency range. Such variants of thesimpler arrangements referred, t6 above will be mere fully explainedhereinafter.

In all forms of" the invention the resonant length oi the. driven dipoleis about three times, or a highei integral multiple of the resonantlength of the added, non-driven dipole or dipoles; and the space betweenthe driven end non-driven dipoles is from about 11% to about 7% of a allength a e w operating, trc vency to h c the driven po s e a am-v henthe driven dip lc. a half-wave long at the low resonant firequeneyfgfwhich h array is d gn d, nd the en-clr vea s ip le is a v; wave longat the higher resonant frequency 'for which the a r y is es gne a co dto he Prefer e orms of th n n n for t s n the r ven dicql i all? th ee ms the ng h of he non-d en (l mb? o dipoles; he a te i c r l y ali ne ithe farmer when each is sid to a s gn l o be re ei ed; and the spa e between e en and non-dr en. dipoles i abou to ou of the hall e eson nt lng h f th riven po e, which is oughly i s p ysi al. l ngth hen usconductors having L D r tio o 49 qt hi hen he? tab y n i as the U13 ratiis at le st 8 a may be as re 6D o mo e, and h sp in 01 e dr ven andnon-driven dipoles in this case is preferably bou 1% o about 5% of he nh o the r v n pol In a l rms o t e inv nti n he dded nandiives elementshave little effect on the operation of the driven emen at o near hefrequen y a vvluc i is re onan in h 1QW eq en y ange- Hqw vsr, at a hiher i s q y at which the ed, nan-dr ven element e sona as half-waveelements they hav PI DP QGE favorable efiec s on i he the impedanc o theradiation p t n o h antenna or b t i In ea h ca u he impro ement may hob a n d. b the u o conventional ct rs and r refl ctors, number ofnon-driven elements, the lengths of the driven and non-driven elements,the lengths oi the directors and/or l t s, th ir pac ng from the dri n.eleme and the diameters of the driven and non-driven elements in e n oeir en t may va be a just d o va y th impedance of t e ent a y in the.la; and hi h and and to adjust the equ n e Q 5 spou e in the low a h ads o e s it t e particular ne ds to be filled.

While the e ti n ha b en discus ed abo e Pri aril in relation to theproblems of television reception, it vvillv b pp ia hat the Princip esemploye a q al y useful n the solu on of othe rad o rcauency receptionproblems. Thus, the, invention will be fo nd to be pp ica to anyituations h ch i desire to pl y the s m nna in widely sepa ated freque yranges and/or o rende it les f eque cy sensitive- W t the o o ng en rall$1ll0ll in mind the e t n il be be ter understood. t am the detaileddescription of a number of illustrative menls o th n en on, consi re toeth r w th p nyi s drawings, n Wh 1l- Figure 1 s a a mmat c pe spectiveew o a d d dipole and a straight d pol anged i accor ance withinvention;

la 2 i a d a r m t c pla w o the dipole a rangement of Fig. l;

Figure 3 is a i g ammati p a e of a straigh driven dipole with twoadded, non-driven dipoles; v

Fig. 4 is a diagrammatic plan view of a straight, driven dipole withthree added, non-driven dipoles;

Fig. 5 is a diagrammatic perspective view of a straight, driven dipolewith a single, added, non-driven dipole;

Fig. 6 is a perspective view of an antenna erray em driven dipole, and areflector disposed behind the driven dipole; Fig. 7 is a foreshortenedplan View, on an enlarged scale, of the antenna of Fig. 6;

Fig. 8 is a plan view, on a reduced scale, of a modification of theantenna of Figs. 6 and 7;

Fig. 9 is a fragmentary front elevation, on an enlarged scale, of bothforms of the invention illustrated in Figs. 6 to 8;

Fig. 10 is a vertical section through the structure shown in Fig. 9, theplane of the section being indicated by the line 10-10 in Fig. 9;

Fig. 11 is a fragmentary vertical section showing one form of insulatingsupport forthe driven dipole of both forms of the invention illustratedin Figs. 6 to 8, the

plane of the section being indicated by the line 11-11 in Fig., 6; i

larged scale, of the non-driven element in one of the bays of theantenna of Fig. 12, showing how it is mounted with respect to the drivenelement;

Fig. 14 is a vertical sectional view of the structure shown in Fig. 13,the plane of the section being indicated by the line 14--14 in Fig. 13;

Fig. 15 is a fragmentary, vertical, sectional View of the antenna shownin Fig. 12, the plane of the section being indicated by the line 15-15in Fig. 12;

I Fig. 16 is a typical graph showing the voltage standing wave ratio ofone bay of the antenna of Figs. 12 to 15, plotted against frequency;

Fig. 17 is a plan view of a simple form of the invention, like that ofFig. 5, but made of hollow tubing;

Fig. 18 is an end elevation of the antenna of Fig. 17;

Fig. 19 is a polar diagram showing the horizontal radiation pattern ofthe antenna of Figs. 17 and 18 in the frequency range of 175 to 185rnc.;

Fig. 20 is a plan view of the same antenna as Figs. 17 and 18, but withan additional non-driven dipole added thereto;

Fig. 21 is an end elevation of the antenna of Fig. 20;

Fig. 22 is a front elevation of the antenna of Figs. 17 and 18 afterbeing rotated 90 about the longitudinal axis of the driven dipole toposition the non-driven dipole vertically above the driven dipole;

Fig. 23 is an end elevation of the antenna of Fig. 22; and

Fig. 24 is a polar diagram showing the horizontal radiation pattern ofthe antenna of Figs. 20 and 21 and also of the antenna of Figs. 22 and23.

Referring first to the embodiment of the invention illustrateddiagrammatically in Figs. 1 and 2, an elongated folded dipole 1 and amuch shorter, straight dipole 2 are disposed in closely spaced parallelrelationship. To assist in visualizing the spacial relationship of thetwo dipoles, a horizontal axis AA is shown in Fig. l to represent a linefrom the antenna to the source of a signal to be received; a secondhorizontal axis BB, normal to the axis AA, represents the longitudinalaxis of the folded dipole 1; and a vertical axis V-V represents thetransverse axis of the folded dipole 1, the two long portions or spansof the folded dipole being disposed one above the other in a verticalplane containing the axis V--V. The short dipole 2 is disposed centrallyin front of the long dipole 1, with respect to a signal to be received,and is bisected by the horizontal axis AA. The length of the long dipole1 is represented by the dimension L, and the length of the short dipole2 is one-third the length L of the long dipole, as indicated by thedimension L/3. The long dipole 1 is a driven element and is connected toI I a two-conductor transmission line as indicated by the leads 3; Theshort dipole 1 is non-driven.

For television reception over the low and high band frequencies, thedriven and non-driven elements of the antenna of Figs. 1 and 2 maydesirably be made of aluminum tubing up to say, /2 inch in diameter ormay suitably be made of smaller diameter rod down to 4;" diameter oreven smaller. Since the length L would normally be at least inches, andpreferably more, it will be observed that the L/D ratio would be in therange of from around to as high as 1000 for the driven element. Sincetubes larger than 1 inch in diameter would seldom be desired forcommercial television antenna elements, the driven element of theantenna of Figs. 1 and 2 would normally have These same factors willaffect the optimum spacing of i the two dipoles, indicated in Fig. 2 bythe dimension S. In general, the smaller the diameter of the conductormaterial of which the dipoles are constructed, the smaller is thedimension S, other factors being equal. As noted above, the dimension Sis adjusted to obtain the optimum impedance match at about three timesthe half-wave resonant frequency of the folded dipole 1, the impedanceof the antenna being progressively reduced as the dimension 5 isdecreased.

In this connection, it should be noted that the driven folded dipole 1preferably has its long parallel spans disposed in a plane normal to thepath AA of a signal to be received, as shown in Fig. 1, and the spacingof the driven and non-driven elements 1 and 2 is measured along thesignal path AA. However, the driven folded dipole 1 may have its longparallel spans disposed substantially in a common plane with the addednon-driven element 2, or in some other plane. In such case, surprisingas it may be, the critical spacing S is the distance between the addednon-driven element 2 and the span of the folded dipole 1 to which theleads 3 of the transmission line are connected, measured along thesignal path AA, regardless of which of the two long spans of the foldeddipole 1 is closest to the non-driven dipole 2. References in theappended claims to the spacing between a driven folded dipole and anadded non-driven dipole are intended to be interpreted accordingly.

When operating at the relatively low half-way resonant frequency of thefolded dipole 1, the presence of the short dipole 2 has little effect,and the instantaneous current in each of the upper and lower spans ofthe folded dipole may be represented by the dotted curve 1;, in Fig. 2.However, when operating at about three times that frequency, theindicated mode of operation (judged by the impedance at the terminals 3,the forward gain, and the shape of the radiation pattern in the twoforward quadrants) produces instantaneous currents in each of the upperand lower portions of the folded dipole 1 which appear to consist ofthree in-phase components represented by the dotted curves I In thesecurrent representations, it will be understood that the curves areintended to represent relative wave lengths or frequencies, but not therelative magnitudes of the current.

gain as a collinear array of'three half-wave elements connected togetherfor in-phase operation {as by quarterwave, shorted stubs) and center'fed :as a unit-by 21 mm conductor transmission line. Since :a pluralityof'parallel, coextensive, closely spaced conductors may function .as aresonant transmission line section, they may be substantiallynon-radiating when properly energized. Theamount of radiation emanatingfrom a section .of transmission line maybe reduced by reducingthespacing of :the conductors constituting the section. Within themaximum limit of the spacing of'driven and non-driven dipoles hereindisclosed, using conventional moderateor high ,Q conductors, thecoextensive sections of drivenand non-driven dipoles approximate aresonant transmission line section and, hence, the radiation of one,tends to counteract :or cancel the radiation ofthe other. The-extent towhich the parallel, coextensive line sections approach an idealtransmission line section .depends-inpart upon their-spacing and isgenerally enhanced as the spacingis reduced within the range hereindisclosed.

Thus, in the antenna of Figs. 1 and 2, ,it now appears that the centralcurrent loop I may beabsent entirely or so greatly minimized (whetherin-phaseor .outeofephase) as to have littleefiect on the operation ofthe antenna at the half-wave resonant frequency ofthernon driven dipole2. In this way, the antenna may'be said =t function at the latterfrequency so as to produce the :eflect of two center-fed, half-wavedipoles spaced at half wave apart in a collinear array and driven inphase.

At the low, half-Wave, resonant frequency of the folded dipole 1, theimpedance at the terminals 3 is substantially the normal 300 ohms. Bypropcradjustmcnt of .the spacin g S, the impedance of ,the antenna atabout three times.

that 'low frequency can also -be brought @to substantially 300 "ohms,while achieving the other characteristics of a three-clement collineararray referred to above. By reason-of the fact that these low and highoptimum frequencies are in the ratioof about 1 :3, 'the .antenna'may bedesigned to have its two optimum operating frequencies close to themiddle of the low and high television bands, respectively, at say '65Inc. and 195 Inc.

When so designed, the antenna of Figs. 1 and 2 will maintain a very goodstanding wave ratio over the low and high band frequcncyrangcs, whichratio will depend somewhat :onthc various dimensional considerationsdiscussed abovc. Between the low andhigh'band frequency ranges, andabove and below -those ranges, however, the standing wave ratio risesvery rapidly -to exceedingly high values. Thus, thisantcnna has thc verydesirable tendency to discriminate against signals outside the tworanges of frequencies for which it is. designed.

Referring-now to the form :of the invention shown in Fig. 3, anelongated, driven, straight dipole 4, having a length L may have twoidentical, relatively short, nondri-ven, straight dipoles 5, disposed infronto'f it, parallel thereto, and in longitudinally spaced relationshiprelative to each-other. Each of :the short, non-driven dipoles is aboutthe length of the long, :dri-ven dipolc l, and they are spaced from eachother a;distancc about equal to their individual lengths, as indicatedby the dimension L75. Thus, alternate fifths of the length of the longdipole 4 have short dipoles 5 disposed in front thereof withres'pcct toa signal to be received. The conductor materials are preferably in thesame conventional range of diameters as the antenna of Figs. 1 and 2 foruse in the television frequency ranges.

In this case, the long dipole .4 may be operated as a full-wave dipoleat a relatively low frequency, and the presence of the added shortdipoles 5 will have littlccflect. At about 2 /2 times this lowfrequency, however, the added short dipoles 5 function ,to provide alarger forward lobe in the radiation pattern and to reduce the lobes atother angles, thus improving the performance at the higher I closer to300 ohms. The low and high optimum freq'ucrl dies for the antenna -o'fFig. '3 are the ratio {of atom 1:: 2%or2:5. Thus, this antenna maybedesigned to have its two optimum operating f equencies in the upper halfof the *lo-W telvision band andnear the middle of the television band,respectively, at say 78 me. and 195 ine.

Referring "now to the form of the invention shown in Fig. 4, thesignificant diffcrcnccsfr'om the antenna of Fig. 3 are that three short,non-driven dipoles 5 are employcd, each being one-sixth the length ofthe long, straight, driven dipole 4. The two outer dipoles 6 arelongitudinally spaced apart a distance abouttwic c the'ir individuallengths, and the third di-pole is disposed mid v'v'ay between the outerpair. At the fu-llwave resonant frequcnc'y of the driven dipole 4, theadded non-driven dipoles have little effect. A t the half-wave resonantfrcqucncy of the added non-drive'n dipole's 6 (about 3 the lowerfrequency), the radiationpattern of driv'en dipole 4 above would havefour major lobes at '45, 225, and 315 positions and two smaller lobes atthe 0 and 180 positions. Addition of the 'three hondrivcn elements 6,however, practically eliminates all but the 0 lobe, which isconsiderably enlarged. In addition, the impedance at the high frequencymay be brought cl'o'se t'o 3 60 ohms.

In this case, the optimum =lo'w and high operating frequcncics are inthe ratio of a b'out 1:3, as is dhe case with the antenna of Figs. 1 and2, and these optimum frcque'ncics may also be located substantially inthe middle of the 'low and high television bands, respectively.Rc'tcntion of the centr-a l non-drivcn'ol'cmcht 6 without the prescn ceof =the two outer non-driven elements 6, produces very similar resultsthough 0' lobe in the radiation pattern is somewhat broadened andforcshortencd at a given signal-strength.

Referring next to the antenna of Fig. '5, the invention is illustratedas applied in its simplest form to -a straight driven dipole .7,designed for operation as a half-wave element KO-H low band, instead ofto a folded half-wave driven dipole 1, as in the antenna of Figs. 1 and2. As in Figs. 1 and 2, a single, straight, hon-driven dipole 8 iscentrally disposed in closely spaced relationship in front of the drivendipole 7. Except for "the fact that the driven straight dipole 7 has alower impedance than a folded dipole of the same length, when they areoperating essentially as half-wave elements, the mode of operation isessentially thc'same as for the antenna of Figs. 1 and 2, and the designconsiderations are also generally the same. As previously noted, the rowimpedance of this antenna renders "it less suitable for relevisionreception than the forms of the antennas previously described, thoughits physical simplicity is an advantage. For other radio froqucncyreception purposes, however, it has obvious dcsirable attributes. v

As .is the case *with the antenna of Figs. 1 and '2, the

optimum spacing -S between the driven and nondriven dipoles =in each ofthe antennas of Figs. 3 to 5 will depend in'practice upon permissiblevariations in the other physical dimensions of the antennas. However,when using any of the moderate Q and high Q conductor materials commonlyemployed for "dipole antennas, this spacing should fall within 'therange of about 1% to about 7% of a half-wave length at the low frequencyin the low range to which the driven dipole is resonant, and ispreferably from about 1 to about 5% thereof.

The foregoing description of diagrammatically illus trated forms of theinvention treats the mode of operation of the antennas in an idealizedmanner, as will be recognized by those skilled in the art. When theinvention is applied in practice, however, the described characteristicsand modes of operation, or apparent modes of operation, are more or lessclosely approximated according to the particular service or commercialneeds to be served. To further illustrate the invention, therefore, anumber of illustrative, commercially practical antenna designs will nowbe described.

, 11 Referring to the form of the invention illustrated in Figs. 6, 7,and 9 to 11, a single bay antenna embody ng the present invention isshown, the several figures being drawn approximately to scale. Theconstruction shown utilizes a single, long, rigid, tubular element 11both as the main supporting cross-arm for the antenna structure and as aparasitic reflector, generally in accordance with U. S. Patent No.2,630,531 to Lewis H. Finneburgh, Jr. The reflector 11 may be secureddirectly to a vertical mast 12 by means of a conventional U-bolt 13 andsaddle 14, the U-bolt embracing the mast 12 with its legs passingthrough the saddle 14 and reflector 11 so as to restrain the reflectoragainst rotation about its own longitudinal axis. A pair of nuts 13 maybe applied to the two legs of the U-bolt and tightened against thereflector 11 to clamp the assembly securely to the mast 12. 1

A plurality of outer minor cross-arms 17 and a central minor cross-arm18 are suitably secured to the reflector 11 so as to extend forwardlyand horizontally in parallel relationship as cantilever supporting arms.At their forward ends, the minor cross-arms 17 have suitable insulatorssecured thereto for supporting the outer portion of a driven dipole,hereinafter described, the driven dipole being spaced about of itslength from. the refiector 11. The central minor cross-arm 18 passesthrough and beyond a generally triangular insulator 21 which supportsthe central portion of the driven dipole.

The driven dipole, generally designated 22, preferably of the foldeddipole type, may comprise an elongated loop having upper and lowerparallel spans 23 and 24. The upper span 23 of this dipole iselectrically continuous from one outer extremity to the other, whereasthe lower span 24 has a central gap bridge by the triangular supportinginsulator 21. This central gap serves as a conventional feed gap in themanner hereinafter described. The outer extremities of the upper andlower spans 23 and 24 of the dipole 22 are integrally connected byshort, rounded, end portions 25 of the dipole loop.

For convenience in assembling and mounting the dipole 22, it may beconstructed of relatively small diameter rod e. g. about inch, formedinto identical right and left, half-loop portions having their innerfree ends bent back upon themselves to form founting eyes 26. Themounting eyes 26 of the upper dipole span 23 are overlapped inalignment, and a screw 27 passes through these aligned eyes and throughthe upper portion of the triangular insulator 21 into a short supportingtube 28. The supporting tube 28 is disposed parallel to and iscoextensive with the forward end portion 29 of the central minorcross-arm 18, which projects continuously through the triangularinsulator 21. The interior of the short supporting tube 28 may be tappedto receive the screw 27 for tightening this portion of the assembly. Thecorresponding eyes 26 formed on the free ends of the lower portion 24 ofthe dipole 22 are separately secured to the triangular insulator 21 inhorizontally spaced relationship by means of a pair of screws 31 andnuts 32, which also serve as terminals for the leads 33 of atwocondu-ctor transmission line.

For convenience in assembly, the supporting insulators referred to aboveas being mounted on the forward ends of the outer pair of minorcross-arms 17 may be formed in two parts 35 and 36 as shown in Fig. 11.Upper and lower aligned grooves may be formed in the adjacent faces ofthe two parts 35 and 36 to receive the upper and lower portions 23 and24 of the dipole 22. Screws 37 may be passed through apertures in thecenters of the insulator pieces 35 and 36 and be threaded into theforward ends of the outer minor arms 17 for clamping this assemblysecurely together. Alternatively, a single insulator block may beemployed and be drilled to form a pair of apertures through which theportions 23 and 24 of the dipole 22 may be threaded before forming theeyes 26 thereon.

A generally triangular mounting plate 40, preferably 12 a formed ofconductive sheet metal, is mounted on the forward ends of the shortsupporting tube 28 and the extension 29 of the central minor cross arm18 for supporting a non-driven dipole element 42. In this embodiment ofthe invention, the non-driven dipole element is a single straight pieceof hollow metal tubing of, say, inch to /2 inch outside diameter. A pairof spaced supporting flanges 43 may be struck out from the lower edge ofthe metal supporting plate 40 to assist in maintaining the dipole 42 inhorizontal, parallel alignment with the driven dipole 22. This portionof the assembly may be held rigidly together by means of a pair ofscrews 44 and 45, respectively threaded into the forward ends of thetubular supports 28 and 29, the screw 45 passing through the center ofthe tubular dipole 42, as best shown in Figs. 9 and 10.

Depending upon the particular frequencies at which maximum response isdesired in the low and high band ranges, the dimensions and relativeproportions of the various parts of the particular antenna illustratedin Figs. 6, 7, and 9 to 11 may obviously be varied over a considerablerange. The optimum spacing of the nondriven element from the drivenelement (indicated by the dimension S in Fig. 2) for producing animpedance as close as possible to 300 ohms at some frequency in both thelow and high bands will depend upon an even greater number of factorsthan is the case with the simpler antennas of Figs. 1 to 5. As will berecognized by one skilled in the art, in addition to the physicaldimensions of the driven and non-driven dipoles themselves, thesefactors include the diameter and length of the reflector tube 11, thelength of the metallic minor cross-arms 1'7 and 18 (which affect theoptimum length of the reflector 11), the spacing between the foldeddipole 22 and the reflector 11, and other design details which will havegenerally understood influences on the various electricalcharacteristics of the array as a whole.

As previously indicated, the spacing S affects the impedance of theantenna when operating in the high band range of frequencies, though ithas very little effect when operating in the low band range. Therefore,this dimension may be adjusted experimentally to the optimum value forobtaining the best possible match of the impedance of the antenna to theimpedance of the transmission line in the high band frequency range. Foroptimum results, this dimension S in the antenna of Figs. 6, 7, and 9 to11 should be from about 1% to about 5% of a half-wave length at the lowfrequency to which the driven dipole 22 is resonant as a half-wavedipole, depending on the several variable factors referred to above.

As mentioned above, it is preferred that the center of the non-drivendipole be connected to ground. Also, as is customary in the art, thecenter point of the upper span of the driven folded dipole 22 (a pointof zero voltage) is desirably grounded as a protection againstlightning. It will be apparent from the drawings and the foregoingdescription that these two points on the driven and non-driven dipolesare electrically connected to each other through the metal plate 40,screw 44, supporting tube 28, and screw 27. It will also be apparentthat both are electrically connected to the mast 12 through the centralminor cross-arm 18, reflector 11, and U-bolt and saddle 13 and 14.Therefore, the desired grounding of the two dipoles requires merely thatthe mast 1.2 be grounded in any suitable manner.

Referring now to the modification of the invention illustrated in Fig.8, the only significant difference from the antenna of Figs. 6, 7, and 9to 11 is that the folded dipole 22a, viewed in plan, is bent inwardly,as shown in Fig. 8. This is done in order to position the non-drivendipole 42 substantially in the same vertical plane as the outerextremities of the driven dipole 22a, with the dimension S remainingessentially the same as before over most of the length of the non-drivendipole 42. This modification also requires that the central minor crossarm 1821 be correspondingly shortened so that it has approximately thesame overall length as the outer-minor cross arms 17. In all otherrespects, the construction of the antenna illustrated in Fig. 8 may beidentical with that illustrated in Figs. 6, 7, and 9 to 11.

The advantage of the modification of the invention illustrated in Fig. 8resides in the fact that the addition of the non-driven dipole 42 doesnot increase the overall dimensions of the antenna, and the entireassembly may be packaged in a carton no larger than would be required ifthe non-driven dipole 42 and the additional supporting structuretherefor were entirely omitted. The changes made in securing thisadvantage undoubtedly have some effect upon the various electricalcharacteristics of the antenna, but this efiect is small and can becompensated by proper adjustment of the other dimensions.

Referring next to the embodiment of the invention shown in Figs. 12 to15, an arrangement of four stacked antenna arrays or bays is illustratedin which each bay is generally similar to the one illustrated in Fig. 8.The four bays are vertically spaced and interconnected in parallelthrough a feeding circuit to the leads 33' of a two-conductortransmission line. In this embodiment of the invention, however, thenon-driven dipoles 42a have been given the configuration of elongatedloops in order to increase their efiectiveness over a broader frequencyrange. This will require some readjustment of the spacing between thedriven and non-driven dipoles to maintain the desired impedance and ofthe length of the nondriven dipole 42a to maintain the same optimumfrequency of operation in the high frequency range. In practice, withthe particular design illustrated, the spacing averages about 2 to 3% ofthe half-wave length in the low freqnency range to which the drivendipole 22a is resonant, being somewhat greater at the center than at theends of the non-driven dipole 42a.

Except for additional minor changes in the structure for supporting thismodified non-driven dipole, described below, each bay of the antenna ofFigs. 12 to 15 is the same as the antenna of Fig. 8 and each bay issimilarly mounted on the mast 12, as indicated by the use of the samereference characters on corresponding parts. For simplicity ininterconnecting the upper and lower pairs of bays, however, alternatebays are inverted with respect to the other bays to which they arerespectively directly connected.

As most clearly shown in Figs. 13 and 14, the elongated loop of thenon-driven dipole 42a is made in right and left halves out of smalldiameter metal rod. Each half of this dipole has the ends of its twolegs bent to form eyes 51 for receiving mounting screws. The two eyes 51of one-half of this dipole are respectively overlapped in axialalignment with the corresponding eyes 51 of the other half of thisdipole, as shown in Fig. 14. A fiat metal stn'p 40a is employed toconnect the forward end of the short supporting tube 2.8 to the forwardend of the portion 29 of the minor cross arm 18a. A screw 52 passesthrough the upper overlapped pair of eyes 51, through the metal strip40a, and into the short tube 28 in threaded engagement therewith.Another screw 53 passes through the lower overlapped pair of eyes 51 andthrough the metal strip 40a, and is threaded into the portion 29 of 'theminor cross arm 18a. Tightening of the twoscrews 52 and 53 rigidifiesthis relatively light weight portion 'of the assembly and holds theseveral parts in alignment as shown.

Since the modified non-driven dipole 42a is an electrically continuous,closed loop, and is shorted across the mid-points of the upper and lowerspans of the loop, it actually functions as a simple dipole and onlysuperficially resembles a folded dipole in appearance. Its advantagedipoles 42, is that the loop- 42a simulates the electrics! effect of aflat sheet of conductive material having theperipheral outline of theloop and maintains its effect over a broader frequency range.

As will be apparent, both the driven and non-driven dipoles in each bayof this antenna array are effectively grounded merely by grounding themast 12, as is also the case with the previously described forms of theinvention.

When stacking four such bays as illustrated in Fig. 12, the second andfourth bays are inverted so that the transmission line terminal screws32 are on the upper span rather than on the lower span of these twobays. A pair of parallel, vertical, feeder conductors 55 respectivelyconnect the terminal screws 32 of the uppermost bay to the oppositeterminal screws 32 of the next lower bay; and the two lowermost bays aresimilarly connected together. Desirably, each of the vertical conductors55 is made as two separate pieces 55a and 55b (Fig. 15) havingoverlapped eyes 56a and 56b where they are joined midway between thebays for receiving terminal screws 57 carried by a spacing insulator 58.This enables each interconnected pair of bays to be collapsed with aparallelogram type of folding action, generally in accordance with U. S.Patent No. 2,630,531 to Lewis H. Finneburgh, I r.

The upper pair of bays is connected in parallel with the lower pairof'bays by a pair of vertical conductors 60, which may be curved attheir upper and lower ends, as shown in Fig. 12, and are respectivelyconnected to the terminal screws 57 at the midpoints of the verticalfeeders 55. The curving of the conductors 60 is for the purpose ofgiving them the desired overall length for matching the impedance of theentire array to the impedance of the transmission line in a well knownmanner. For simplicity of illustration, additional insulator supportsfor the curved vertical conductors 60' have been omitted.

To illustrate the performance characteristics of the antenna of Figs. 12to 15, and, at the same time, to demonstrate the manner in which theinvention assists the performance in the desired frequency ranges andthe rejection of signals outside those ranges, reference may be made tothe typical voltage standing wave ratio curve shown in Fig. 16 for onebay of the four bay antenna of Figs. 12 to 15 (without the reflector)when connected directly to a 300 ohm transmission line. The curve ofFig. 16 was drawn from standing wave ratio data measured with aMega-Match instrument manufactured by Kay Electric Co. Though thisinstrument tends to exaggerate somewhat the measured S. W. R. valuesgreater than about 3, so that the high values indicated by the curve aresomewhat too high, the characteristics of the array are shown by thecurve with reasonable accuracy. As may readily be seen, the standingwave ratio rises rapidly between and beyond the low and high bandfrequency ranges. From this it is clear that the array is highlyselective to frequencies in the desired ranges and has relatively littletendency to receive signals in adjacent frequency ranges, particularlythe intermediate range of 88 to 174 mc. presently allocated to amateur,government, and commercial radio broadcasting.

For a more complete understanding of the factors affecting theperformance of the various forms of the invention shown in Figs. 6 to15, a discussion of the impedance matching problems will be helpful.When isolated from any reflector, director, or metallic supportingstructure, a single folded dipole, at its half-wave resonant frequency,has an impedance of substantially 300 oms and, therefore, matches theimpedance of a standard 300 ohm transmission line. It also has a figure'8 radiation pattern. Over a fair range of frequencies above and below,the half-wave resonant frequency, the departure .of the impedance ofthe folded dipole from 300 ohms is .not so great as to seriously reducethe transmission of energy ,to

the transmission line, and the radiation pattern changesvery little.Thus, when dimensioned for about the center of the low band offrequencies, a folded dipole will serve with satisfactory efliciencyover the entire low band.

Placing a much shorter, non-driven dipole centrally in front of a lowband folded dipole, with close spacing in accordance with the presentinvention, has so little efiect on either the impedance or radiationpattern of the antenna in the low band range that the effects arenegligible insofar astelevis'ionr'eception is concerned.

When a single, isolated, driven folded dipole, dimensioned for low bandis operating in the high band range, however, its impedance rises toaround 450 ohms, depending on the particularfrequency of operation inthe high band. Also, its radiation pattern is essentially a s mmetricalfour leaf or six leaf clover pattern with four fn'ain lobesj disposed atabout 45 to 55 to either side of the and 180 positions; In this highband range, the added, non-driven dipole of about /2; the length of thefolded dipole, spaced centrally in front of the folded dipole a distancebetween about 1% and 7% of a half wave length to which the driven dipoleis resonant has 'a very pronounced elfect on both the impedance andradiation pattefn of the antenna.

, By adiusting the spacing of the driven and non-driven dipoles withinthe approximate limits specified, the impedance of the antenna at afrequency in the high band range can be adjusted to substantially 300ohms and will maintain a satisfactory value over a range of frequenciescomparable to the frequency range of the entire high band. At the sametime,- the radiation pattern is changed to provide a large, narrowforward lobe,- with only rela- 'tively small minor lobes at otherforward angles. Significantly, without a reflector, the array has afavorable front-to-back ratio on high band which varies with frequency.The particular frequency at which these results are most completelyachieved in the high band range will vary, of course, with the lengthsof the driven and non-driven dipoles.

When considering the use of reflectors and the stacking of a pluralityof bays to obtain increased gain, many complicating factors areintroduced which, as in any case of commercial antenna design, requirethe balancing of one effect against another to arrive at the finalrelationship considered to be optimum for the particular purpose to beserved.

In the case of the antennas shown in Figs. 6 to 15, for example, thelong reflector 11, relatively closely spaced behind the driven foldeddipole, is a compromise between a low band reflector and a high bandreflector (low band length with high band spacing), and the choice as toits length and its spacing from the driven element involves not only itseffect on the gain of the antenna, but also its substantial effect onthe impedance of the antenna, both on low band and high band.

In the case of the stacked array of four bays shown in Fig. 12, theeffect of the reflectors 11 on the impedance of the individual bays alsogoverns the design of the impedance matching circuit so as to producethe optimum match of the entire antenna array to the transmission line33. Another factor to be considered in this connection is the optimumspacing of the individual bays from each other for both low band andhigh band operation, and the limitation on the vertical height of theentire array imposed by practical, commercial installation problems-Here again, the particular stacked array shown in Fig. 12 represents asatisfactory compromise and balancing of various factors. Obviously, byadding one or more directors to each individual antenna bay shown inFigs. 6 to 15, still further practical performance improvements may beachieved, though with some structural complication of the antennas.

Finally, to illustrate more clearly the effect of a change in theposition of a non-driven dipole by moving it to different positionsabout the axis of the driven dipole,

and the effect of using a plurality of transversely aligned non-drivendipoles, reference is made to Figs. 17 to 24.

Figs. 17 and 18 are plan and end elevations of a driven dipole 70, thatis 84 inches long, and has a non-driven dipole 71, that is 28 incheslong, disposed centrally in front of it with respect to a signal to bereceived, both dipoles being made of inch aluminum tubing and beingspaced 2 inches apart. Transmission line leads 73 feed the driven dipole70. Over the frequency range in the high band of about to 185 me, theradiation pattern in a horizontal plane was an eccentric figure 8 havingits long lobe at 0 and its short lobe at with no side lobes,substantially as shown in Fig. 19. The 0 and 180 directions in Fig. 19are indicated by arrows in Fig. 18. This demonstrates the front-to-backratio of such an array, referred to above. Above and below thisfrequency range, small side lobes develop slowly with an increase ordecrease in frequency, and the front-to-back ratio slowly increases. Theoptimum frequency range can be adjusted up or down by adjustment ofdimensions, as explained above.

Figs. 20 and 21 are plan and end elevations of the same antenna as Figs.17 and 18, but with an additional non-driven dipole 72, identical withthe non-driven dipole 71, added in transversely aligned relationshiptherewith and spaced 2 inches behind the driven dipole 70.

Figs. 22 and 23 are front and end elevations of the same driven dipole70 of Figs. 17, 18, 20, and 21, but with a single non-driven dipole 71a,identical with the non-driven dipoles 71 and 72 mentioned above,disposed directly above the driven dipole 70 with respect to a signal tobe received.

Fig. 24 shows the radiation pattern of both of the arrays of Figs. 20and 21 and Figs. 22 and 23 over the range of 175 to me. The 0 and 180directions in Fig. 24 are indicated by arrows in both Fig. 21 and Fig.23. Over the frequency range, both of these arrays have practicallyidentical radiation patterns substantially as shown with no side lobesand no front-to-back ratio. Above and below this range, small side lobesdevelop slowly, but there continues to be no front-to-back ratio.

Essentially the only differences between the performance of the array ofFigs. 20 and 21 and the array of Figs. 22 and 23 is that the additionalnon-driven dipole in the former tends to give the array a somewhat lowerimpedance in the high frequency range, and side lobes in the radiationpattern develop in size at a somewhat slower rate above and below theoptimum range as regards radiation pattern. Thus, by using two or morenon-driven dipoles distributed in a generally cylindrical array(approaching a cylinder as more are added), and by adjusting theirspacing from the non-driven dipole, a greater measure of control isobtained over the impedance of the array while retaining essentially thesame radiation pattern. However, as explained above, this isaccomplished at the expense of the desired front-to-back ratio andincreases the complexity, weight, and cost of the antenna compared toone employing only a single, forward, non-driven dipole in accordancewith the invention.

Figs. 17 to 24 also demonstrate that the action of the non-drivendipoles is entirely different from the action of either a director or areflector. Obviously, if the non-driven element 71 of Fig. 19 functionedas a director for radiation coming from the 0 direction at a givenfrequency, it would be the wrong length to operate as a reflector forradiation from the 180 direction, and use of identical non-drivenelements on both sides of the driven element, as in the array of Figs.20 and 21, would tend to produce nulls in the radiation pattern at boththe 0 and 180 positions, whereas this does not occur as cleary shown bythe radiation pattern of Fig. 24. Also, a director is effective onlywhen disposed between the driven element and the source of a signal tobe received, whereas the non-driven element of Figs.

17 22 and 23, disposed 90 out of such alignment, has virtually the sameeifect on the radiation pattern as the pair of non-driven elements 17and 72 in Figs. 20 and 21, which are aligned with the driven element andthe source of the signal to be received.

As will be appreciated from the above descriptions of various forms ofthe invention, a distinguishing characteristic of the invention commonto all forms there of is the close spacing of driven and non-drivendipoles. From the examples described for illustrative purposes, it willalso be appreciated that the driven and non-driven dipoles may havevarious lengths relative to each other. Depending upon the particularpurpose to be served, still other relative lengths of the driven andnon-driven dipoles may be employed with the characteristic close spacingto achieve a variety of desirable impedance characteristics andradiation patterns. Since the optimum values for the spacing of thedriven and nondriven dipoles and their relative lengths in anyparticular, practical antenna depend upon many variables, there can beno simple, empirical formula, if any at all, by which theserelationships can be precisely defined. Thus, it is to be understoodthat the spacings and relative lengths specified above and in theappended claims are necessarily approximate values or ranges of values,and they should be so construed in interpreting the scope of theinvention disclosed and claimed herein.

From the foregoing description of the invention and various illustrativeembodiments thereof, it will be appreciated that I have provided basicantenna arrays having many desirable electrical characteristics fortelevision reception in the fringe areas, and practical embodiments ofsuch arrays that also have the mechanical compactness and simplicitydesired for commercial production. Furthermore, the particularembodiments of the invention disclosed in Figs. 6 to 15 are easily andquickly installed and, when installed, have a high degree of symmetryand an overall appearance which are attractive to the domestic trade towhich such antennas are sold.

This application is a continuation-in-part of my copending applicationSerial No. 502,607, filed April 20, 1955, for Radio Frequency Antennas,now abandoned.

Having described my invention, I claim:

[1. A radio frequency antenna comprising a long driven dipole and ashort, non-driven dipole arranged in closely spaced parallelrelationship, the driven dipole having a length selected to render itresonant as a dipole at least a half-wave long at a first selectedfrequency and having an L/D ratio of at least 40, the non-driven dipolehaving a length selected to render it resonant as a half-wave dipole ata second higher frequency which is substantially a harmonic resonantfrequency of the driven dipole at least three times said firstfrequency, and the spacing of the driven and non-driven dipoles beingfrom about 1% to about 7% of a half-wave length at said first frequency][2. A radio frequency antenna comprising a long, driven dipole and atleast one short, non-driven dipole arranged in closely spaced parallelrelationship, the driven dipole having a length selected to render itresonant as a dipole at least a half-wave long at a first selectedfrequency and having an L/D ratio of at least 40, the non-driven dipoleshaving lengths selected to render them resonant as half-wave elements atapproximately a common higher frequency which is substantially aharmonic resonant frequency of the driven dipole at least three timessaid first frequency, and the spacing of the driven and non-drivendipoles being from about 1% to about 7% of a half-wave length at saidfirst frequency] [3. A radio frequency antenna comprising a long, drivendipole and a short, non-driven dipole arranged in closely spacedparallel relationship, the driven dipole having a length selected torender it resonant as a dipole at least a half-wave long at a firstselected frequency and having an L/D ratio of at least 40, thenon-driven dipole having a length selected to render it resonant as ahalf-wave dipole at a second higher frequency which is substantiallythree times said first frequency, and the spacing of the driven andnon-driven dipoles being from about 1% to about 7% of a half-wave lengthat said first frequency] [4. A radio frequency antenna comprising along, driven dipole and a short, non-driven dipole arranged in closelyspaced parallel relationship, the driven dipole having a length selectedto render it resonant as a halfwave dipole at a first selected frequencyand having an L/D ratio of at least 40, the non-driven dipole having alength selected to render it resonant as a half-wave element atapproximately three times said first frequency, and the spacing betweenthe driven and non-driven dipoles being from about 1% to about 7% of ahalf-wave length at said first frequency] [5. A radio frequency antennacomprising a long, driven dipole and a short, non-driven dipole arrangedin closely spaced parallel relationship, the driven dipole having alength selected to render it resonant as a half- Wave dipole at a firstselected frequency and having an L/D ratio of at least 40, thenonedriven dipole having a length selected to render it resonant as ahalf-wave element at approximately three times said first frequency, andthe spacing between the driven and non-driven dipoles being from about1% to about 7% of the length of the driven dipole] [6. A radio frequencyantenna comprising a long, driven dipole and at least one short,non-driven dipole arranged in closely spaced parallel relationship, thedriven dipole-having a length selected to render it resonant as ahalf-wave dipole at a first selected frequency and having an L/D ratioof at least 40, the non-driven dipoles being transversely alignedsubstantially centrally with respect to the driven dipole and havinglengths selected to render them resonant as half-wave dipoles atapproximately three times said first frequency, and the spacing of thedriven and non-driven dipoles being from about 1% to about 7% of thelength of the driven dipole] [7. A radio frequency antenna comprising along, driven dipole and a short, non-driven dipole arranged in closelyspaced parallel relationship, the driven dipole having a length selectedto render it resonant as a dipole at least a half-wave long at a firstselected frequency and having an L/D ratio of at least 40, thenon-driven dipole having a length selected to render it resonant as ahalf-wave dipole at a second higher frequency which is substantially aharmonic resonant frequency of the driven dipole at least three timessaid first frequency, and the spacing of the driven and non-drivendipoles being from about 1% to about 7% of a half-wave length at saidfirst frequency, and means for mounting said antenna with the non-drivendipole disposed substantially between the driven dipole and the sourceof a signal to be received] [8. A radio frequency antenna comprising along, driven dipole and a plurality of short, non-driven dipolesarranged in closely spaced parallel relationship, the driven dipolehaving a length selected to render it resonant as a half-wave element ata first selected frequency and having an L/D ratio of at least 80, thenon-driven dipoles being transversely aligned substantially centrallywith respect to the driven dipole and having lengths selected to renderthem resonant as half-wave elements at approximately three times saidfirst frequency, said non-driven dipoles being spaced apart about thelongitudinal axis of the driven dipole and spaced therefrom at distancesfrom about 1% to about 5% of the length of the driven dipole] [9. Aradio frequency antenna comprising a long, driven dipole and a pluralityof short, non-driven dipoles arranged in closely spaced parallelrelationship, the driven dipole having a length selected to render itresonant as a half-wave element at a first selected frequency and havingan L/D ratio of at least 80, the non-driven dipoles being transverselyaligned substantially centrally with respect to the driven dipole andhaving lengths selected to render them resonant as half-wave elements atapproximately three times said first frequency, said non-driven dipolesbeing spaced apart about the longitudinal axis of the driven dipole andspaced therefrom at distances from about 1% to about 5% of the length ofthe driven dipole, and means for mounting said antenna with one of saidnon-driven dipoles disposed substantially between the driven dipole andthe source of a signal to be received] [10. A radio frequency antennacomprising a long, driven, folded dipole and a short non-driven dipolearranged in closely spaced parallel relationship with the non-drivendipole transversely aligned substantially centrally with respect to thefolded dipole, the folded dipole having a length selected to render itresonant as a halfwave element at a selected frequency and being formedof conductor material having an L/ D ratio of at least 40, thenon-driven dipole having a length selected to render it resonant as ahalf-wave element at about three times said selected frequency, and thespacing of the driven and non-driven dipoles being from about 1% toabout 7% of a half-wave length at said selected frequency] [11. A radiofrequency antenna comprising a long, driven, folded dipole and a shortnon-driven dipole arranged in closely spaced parallel relationship withthe non-driven dipole transversely aligned substantially centrally withrespect to the folded dipole, the folded dipole having a length selectedto render it resonant as a halfwave element at a selected frequency andbeing formed of conductor material having an L/D ratio of at least 80,the non-driven dipole having a length selected to render it resonant asa half-wave element at about three times said selected frequency, andthe spacing of the driven and non-driven dipoles being from about 1% toabout 5% of a half-wave length at said selected frequency] [12. A radiofrequency antenna comprising a long, driven, folded dipole and a shortnon-driven dipole arranged in closely spaced parallel relationship withthe non-driven dipole transversely aligned substantially centrall y withrespect to the folded dipole, the folded dipole having a length selectedto render it resonant as a halfwave element at a selected frequency andbeing formed of conductor material having an L/D ratio of at least 40,the non-driven dipole having a length selected to render 1t resonant asa half-wave element at about three times said selected frequency, andthe spacing of the driven and non-driven dipoles being from about 1% toabout 7% of a half-wave length at said selected frequency, and means formounting the antenna with the non-driven dipole disposed substantiallybetween the folded dipole and the source of a signal to be received][13. A radio frequency antenna comprising a long, driven, folded dipoleand at least one short, non-driven dipole arranged in closely spacedparallel relationship, means for mounting said dipoles with the longspans of the folded dipole disposed substantially in a common verticalplane normal to the direction of a signal to be received and with onenon-driven dipole disposed sub stantially centrally between the foldeddipole and the source of a signal to be received, the folded dipolehaving a length selected to render it resonant as a half-wave element ata selected frequency and being formed of conductor material having anL/D ratio of at least 80, each non-driven dipole having a lengthselected to render it resonant as a half-wave element at substantiallythree times said selected frequency, and the spacing of the driven andnon-driven dipoles being from about 1% to about 5% of the length of thefolded dipole] [1.4. A television antenna comprising a driven, half-Wave, folded dipole resonant at a first frequency in the range of 54 to88 megacycles and a relatively short, non-driven dipole arranged inclosely spaced parallel re lationship therewith, means for mounting saiddipoles with.

the long spans of the folded dipole disposed vertically one above theother and with the non-driven dipole disposed substantially centrallybetween the folded dipole and the source of a signal to be received, thefolded dipole being formed of conductor material having an L/D ratio ofat least 80, the non-driven dipole having a length selected to render itresonant as a half-Wave element at approximately three times said firstfrequenc and the spacing of the folded and non-driven dipoles being fromabout 1% to about 7% of a half-Wave length at said first frequency][2:15. A television antenna comprising a driven, half- Wave, foldeddipole resonant at a first frequency in the range of 54 to 88 megacyclesand a relatively short, nondriven dipole arranged in closely spacedparallel relationship therewith, means for mounting said dipoles withthe long spans of the folded dipole disposed vertically one above theother and with the non-driven dipole disposed substantially centrallybetween the folded dipole and the source of a signal to be received, thefolded dipole being formed of conductor material having an L/D ratio ofat least 80, the non-driven dipole being in the form of an elongatedloop the major axis of which has a length selected to render the loopresonant as a half-wave simple dipole at approximately three times saidfirst frequency, and the spacing of the folded and non-driven dipolesbeing from about 1% to about 5% of a half-wave length at said firstfrequency] 16, A radio frequency antenna comprising a rigid rectilinearreflector, a dipole mounted on said reflector and disposed substantiallycentrally in front of the reflector and generally parallel thereto, saiddipole having about the central one third portion of its length offsettoward said reflector, a conductor about one third the length of saiddipole mounted substantially centrally in front of said central portionof said dipole, substantially in alignment with the end portions thereofand spaced from said central portion thereof.

17. A television antenna comprising a rigid rectilinear reflecton'meansfor mounting said reflector broadside to a signal to be received, afolded dipole having a halfwave resonant frequency in the range of 54 to88 megacycles, said folded dipole being mounted on said reflector anddisposed substantially centrally in front of the re flector andgenerally parallel thereto and with the spans of the folded dipole in acommon vertical plane, said folded dipole having about the centralone-third portion of the length thereof offset toward said reflector anddisposed substantially closer to said reflector than are the endportions of the folded dipole, and a conductor about /3 the length ofsaid folded dipole mounted horizontally and substantially centrally infront of said folded dipole and substantially in the same vertical planeas the end portions thereof, said conductor being spaced a distance ofabout 1% to about 7% of the length of said folded dipole from thecentral one-third portion thereof.

18. A television antenna comprising a rigid rectilinear reflector, meansfor mounting said reflector broadside to a signal to be received, afolded dipole having a halfwave resonant frequency in the range of 54 to88 megacycles, said folded dipole being mounted on said reflector anddisposed substantially centrally in front of the reflector and generallyparallel thereto and with the two long spans of the folded dipole in acommon verti plane, said folded dipole having the central portion o thelength thereof offset toward said reflector and posed substantiallycloser to said reflector than are the end portions of the folded dipole,a conductor approXi mately /3 the length of said folded dipole mountedhorizontally and substantially centrally in front of said folded dipole,said conductor being spaced from about 1% about 7% of the length of thefolded dipole from the offset central portion thereof, there being anelectrical connection betweenthe center of said reflector, the center ofone long span of said folded dipole, and the center of said conductorfor grounding the same, and terminals for connecting a two-conductortransmission line to the other long span of said folded dipole.

19. A television antenna comprising a rigid rectilinear reflector, meansfor mounting said reflector broadside to a signal to be received, anelongated folded dipole having a half-wave resonant frequency in therange of 54 to 88 megacycles, said folded dipole being mounted on saidreflector and disposed substantially centrally in front of the reflectorwith its major axis generally parallel thereto and with the two longspans of the folded dipole in a common vertical plane, said foldeddipole having about the central one-third portion of the length thereofoffset toward said reflector and disposed substantially closer to saidreflector than are the end portions of the folded dipole, a conductiveelement in the form of an elongated loop having the length of its majoraxis approximately /3 the length of the major axis of said foldeddipole, said element being mounted with its major axis extendinghorizontally and being substantially centrally disposed in front of saidfolded dipole and substantially in the same vertical plane as the endportions thereof, said element being spaced from about 1% to about 7% ofthe length of said folded dipole from said central portion thereof, andterminals for connecting a two-conductor transmission line to one longspan of said folded dipole.

20. A television antenna comprising a rigid rectilinear reflector, meansfor mounting said reflector broadside to a signal to be received, anelongated folded dipole having a half-wave resonant frequency in therange of 54 to 88 megacycles, said folded dipole being mounted on saidreflector and disposed substantially centrally in front of the reflectorwith its major axis generally parallel thereto and with the two longspans of the folded dipole in a common vertical plane, said foldeddipole having the central portion of the length thereof offset towardsaid reflector and disposed substantially closer to said reflector thanare the end portions of the folded dipole, a conductive element in theform of an elongated loop having the length of its major axis selectedto render said loop resonant as a half-wave element in the range of 174to 216 megacycles, said loop being mounted substantially in a verticalplane with its major axis extending horizontally and being substantiallycentrally disposed in front of said folded dipole and spaced from about1% to about 7% of the length of the folded dipole from the offsetcentral portion thereof.

21. A radio frequency antenna comprising a long driven dipole and asingle, short, non-driven dipole arranged in closely spaced parallelrelationship, the driven dipole having a length selected to render itresonant as a dipole at least a half-wave long at a first selectedfrequency and having an L/D ratio of at least 40, the non-driven dipolehaving a length selected to render it resonant as a half-wave dipole ata second higher frequency which is substantially a harmonic resonantfrequency of the driven dipole at least three times said firstfrequency, and the spacing of the driven and non-driven dipoles beingfrom about 1% to about 7% of a half-wave length at said first frequency.

22. A radio frequency antenna comprising a long, driven dipole and atleast one short, non-driven dipole, each such non-driven dipole beingdisposed in front of the driven dipole with reference to the same singledirection of transmission or reception and arranged in closely spacedparallel relationship with the driven dipole, the driven dipole having alength selected to render it resonant as a dipole at least a half-wavelong at a first, selected frequency and having an L/D ratio of at least40, the non-driven dipoles having lengths selected to render themresonant as half-wave elements at approximately a common higherfrequency which is substantially a harmonic resonant frequency of thedriven dipole at least three times said first frequency, and the spacingof the driven and non-driven dipoles being from about 1% to 2?. about 7%of a half-wave length at said first frequency.

23. A radio frequency antenna comprising a long, driven dipole and asingle, short, non-driven dipole arranged in closely spaced parallelrelationship, the driven dipole having a length selected to render itresonant as a dipole at least a half-wave long at a first selectedfrequency and having an L/D ratio of at least 40, the nondriven dipolehaving a length selected to render it resonant as a half-wave dipole ata second higher frequency which is substantially three times said firstfrequency, and the spacing of the driven and non-driven dipoles beingfrom about 1% to about 7% of a half-wave length at said first frequency.

24. A radio frequency antenna comprising a long, driven dipole and asingle, short, non-driven dipole arranged in closely spaced parallelrelationship, the driven dipole having a length selected to render itresonant as a half-wave dipole at a first selected frequency and havingan L/D ratio of at least 40, the non-driven dipole having a lengthselected to render it resonant as a half-wave element at approximatelythree times said first frequency, and the spacing between the driven andnon-driven dipoles being from about 1% to about 7% of a half-wave lengthat said first frequency.

25. A radio frequency antenna comprising a long, driven dipole and asingle, short, non-driven dipole arranged in closely spaced parallelrelationship, the driven dipole having a length selected to render itresonant as a half-wave dipole at a first selected frequency and havingan L/D ratio of at least 40, the non-driven dipole having a lengthselected to render it resonant as a halfwave element at approximatelythree times said first frequency, and the spacing between the driven andnondriven dipoles being from about 1% to about 7% of the length of thedriven dipole.

26. A radio frequency antenna comprising a long driven dipole and atleast one short, non-driven dipole, each such non-driven dipole beingdisposed in front of the driven dipole with reference to the same singledirection of transmission or reception and arranged in closely spacedparallel relationship with the driven dipole, the driven dipole having alength selected to render it resonant as a half-wave dipole at a firstselected frequency and having an L/D ratio of at least 40, each suchnondriven dipole having a length selected to render it resonant as ahalf-wave dipole at a higher frequency which is substantially a harmonicof said first frequency, and the spacing of the driven and non-drivendipoles being from about 1% to about 7% of the length of the drivendipole.

27. A radio frequency antenna comprising a long driven dipole and asingle, short, non-driven dipole arranged in closely spaced parallelrelationship, the driven dipole having a length selected to render itresonant as a dipole at least a half-wave long at a first selectedfrequency and having an L/D ratio of at least 40, the nondriven dipolehaving a length selected to render it resonant as a half-wave dipole ata second higher frequency which i substantially a harmonic resonantfrequency of the driven dipole at least three times said firstfrequency, and the spacing of the driven and non-driven dipoles beingfrom about 1% to about 7% of a half-wave length at said first frequency,and means for mounting said antenna with the non-driven dipole disposedsubstantially between the driven dipole and the source of a signal to bereceived.

28. A radio frequency antenna comprising a long, driven dipole and aplurality of short, non-driven, collinear dipoles all disposed in frontof the driven dipole with reference to a single direction oftransmission or reception and arranged in closely spaced parallelrelationship with the driven dipole, the driven dipole having a lengthselected to render it resonant as a half-wave element at a firstselected frequency and having an L/D ratio of at least 80, thenon-driven dipoles being longitudinally 23 spaced apart and havinglengths selected to'render them resonant as half-wave elements at asecond higher frequency which is substantially a harmonic of said firstfrequency, said non-drivendipoles being spaced from the driven dipolefrom about 1% to. about 5% of the length of the driven dipole. I

29. A radio frequency vantenna comprising a long, driven dipole and aplurality of short, non-driven dipoles all disposed in collinearalignment in front of the driven dipole with reference to a singledirection of transmission or reception and. arranged in closely spacedparallel relationship with the driven dipole, the driven dipole having alength selected to render it resonant as a halfwave element at. a firstselected frequency and having an L/D ratio of at least 80, thenon-driven dipoles-being longitudinally spaced apart about a half-waveat a second higher frequency which is a harmonic of said first.frequency and all having lengths selected to render them resonant ashalf-wave elements at approximately said higher harmonic frequency, saidnon-driven dipoles being spaced from the driven dipole from about 1% toabout 5% of the length of the driven dipole.

50. A radio frequency .antenna comprising a single, long, driven, foldeddipole and a single, short, non-driven dipole arranged in closely spacedparallel rela ionship with the folded dipole and transversely alignedsubstantially centrally with respect to the folded-dipole, the foldeddipole having a length selected to render it resonant as a half-waveelement at a selected frequency-and being formed of conductor materialhaving an L/D ratio of at least 40, the non-driven dipole having alength selected to render it resonant as a half-wave element at aboutthree times said selected frequency, and the spacing of-the folded andnon-driven dipoles being from about 1% to about 7% of a half-wave lengthat said selected frequency.

31. A radio frequency antenna comprising a single, long, driven, foldeddipole and a single, short, non-driven dipole arranged in closely spacedparallel relationship with the folded dipole and transversely alignedsubstantially centrally with respect to the folded dipole, the foldeddipole having a length selected to render it resonant as a half-waveelement at a selected .frequency and being formed of conductor materialhaving an L/D ratio of at least 80, the non-driven dipole having alength selected to render it resonant as a half-wave element at aboutthree times said selected frequency, and the spacing of the folded andnon-driven dipoles being from about 1% to about 5% of a half-wave lengthat said selected frequency.

32. A radio frequency antenna comprising a long, driven, folded dipoleand a single, short, non-driven'dipole arranged in closely spacedparallel relationship with the folded dipole, the folded dipole having alength selected to render it resonant as a half-wave element at aselected frequency and being formed of conductor material having an L/Dratio of at least 40, the non-driven dipole having a length selected torender it resonant as a half-i-vave element at about three times saidselected frequency, and the spacing of the folded and non-driven dipolesbeing from about 1% toabout 7% of a halfwave length at said selectedfrequency, and means for mounting the antenna with the non-driven dipoledisposed substantially centrally between the folded dipole and thesource of a signal to be received.

5'3. A radio frequency antenna comprising a long, driven, folded dipoleand at least one short, non-driven dipole, each such non-driven dipolebeing disposed in front of the driven dipole with reference to the samesingle direction of transmission or reception and arranged in closelyspaced parallel relationship with the driven dipole, means for mountingsaid dipoles with the long spans of the driven folded dipole disposedsubstantially in a common vertical plane normal to said direction andwith one non-driven dipole disposed substantially centrtilly. withrespect .to the ends of the. folded dipole, the folded dipole'having alength selected-to render it resonant as a half-waveelementiatzsagselectedfrequency and being formed 'of conductor materialhaving van L/D ratio of at least 80, each=non+driven dipole having alength selected to renderit'resonantas a half-wave element atsubstantially three timessaid selected frequency, the 1 non-drivendipoles being longitudinally spaced apart in collinear alignment, andthe spacing of the driven and non-driven dipoles being from about 1%toabout 5% of the length of the driven dipole.

A television antenna comprising a driven, halfwave, folded dipoleresonant at a first frequency inthe range of 54 to 88 megacyclesand asingle, relatively short, non-driven dipole arranged in closely spacedparallel relationship therewith, means for mounting said dipoles withthe long spans of the folded dipole disposed vertically one above theother and with the non-driven dipole disposed substantially centrallybetween the folded dipole and the source of a signal to be received, thefolded dipole being formed of conductor material having an L/D ratioof'at' least 80, the nono-driven dipole having a length selected torender it resonant as a halfwave element at approximately three timessaid first frequency, and the spacingof the folded and non-drivendipoles being from about 1% to about 7% of a halfwave length. at saidfirst frequency.

35. A television antenna comprising a driven, halfwave, folded dipoleresonant at a first frequency in the range of 54 to 88 mcgacycles and asingle, relatively short, non-driven dipole arranged in closely spacedparallel relationship therewith, means for mounting said dipoles withthe long spans of the folded dipole disposed vertically one above theother and with the non-driven dipole disposed substantiallycentrallybetween the folded dipole and the source of a signal to bereceived, the folded dipole being formed of conductor material having anL/D ratio of at least 80, the non-driven dipole being in the form of anelongated loop, the major axis of which has a length selected to renderthe loop resonant as a half-wave simple dipoleat approximately threetimes said first frequency, and the spacing of the folded and non-drivendipoles being from-about 1% to'about 5% of a half-wave length at saidfirst frequency.

36. A radio frequency antenna comprising a long driven dipole and asingle, short, non-driven dipole arranged in closely spaced parallelrelationship, the driven dipole having a length selected to render itresonant as a'dipole at leasta half-wave long at a first selectedfrequencyand having an L/D ratio of ,atleast 40, the non-driven dipolehaving a length selected to render it resonant as a half-wave dipole ata second higher frequency which is substantially a harmonic resonantfrequency of the driven dipoleat least three times said first frequency,and the driven and: non-driven dipoles being insuch close proximity,within the range from about 1% to about'7% of the half-wave length atsaid first frequency, that their coextensive portions comprise aresonant transmission line section, whereby radiation front one issubstantially counteracted by radiation from the other at said secondhigher frequency.

37. A radio frequency antenna comprising a long, driven dipole'andasingle, short, non-driven dipole arranged in closely spaced parallelrelationship, the driven dipolehaving a length selected to render itresonant as a half-wave dipole at a first selected frequency and havingan L/D ratio of at least'40, the non-driven dipole having a lengthselected to render it resonant as a halfwave element at approximatelythree times said first frequency, and the driven and non-driven dipolesbeing in such close proximity, within the range from about 1% to about7% of a half-wave length at said first frequency, that their coextensiveportions comprise a resonant transmission linesection, wherebyiradiationfrom. one is sub- 25 stantially counteractea by radiation from the otherat said second higher frequency.

38. A radio frequency antenna comprising a long driven dipole and atleast one short, non-driven dipole, each such non-driven dipole beingdisposed in front of the driven dipole with reference to the same singledirection of transmission or reception and arranged in closely spacedparallel relationship with the driven dipole, the driven dipole having alength selected to render it resonant as a half-wave dipole at a firstselected frequency and having an L/D ratio of at least 40, each suchnon-driven dipole having a length selected to render it resonant as ahalf-wave dipole at a higher frequency which is substantially a harmonicof said first frequency, each of said non-driven dipoles and thecoextensive portion of the driven dipole being in such close proximity,within the range from about 1% to about 7% of a half-wave length at saidfirst frequency, that they comprise a resonant transmission linesection, whereby radiation from one is substantially counteracted byradiation from the coextensive portion of the other at the frequency ofresonance of the transmission line section.

39. A radio frequency antenna comprising a long, driven dipole and aplurality of short, non-driven dipoles all disposed in collinearalignment in front of the driven dipole with reference to a singledirection of transmission or reception and arranged in closely spacedparallel relationship with the driven dipole, the driven dipole having alength selected to render it resonant as a halfwave element at a firstselected frequency and having an L/D ratio of at least 80, thenon-driven dipoles being longitudinally spaced apart about a half-waveat a second higher frequency which is a harmonic of said first frequencyand all having lengths selected to render them resonant as half-waveelements at approximately said higher harmonic frequency, each of saidnon-driven dipoles and the coextensive portion of the driven dipolebeing in such close proximity, within the range from about 1% to about5% of a half-wave length at said first frequency, that they comprise aresonant transmission line section, whereby radiation from one issubstantially counteracted by radiation from the coextensive portion ofthe other at said harmonic frequency.

40. A television antenna comprising a driven, halfwave, folded dipoleresonant at a first frequency in the range of 54 to 88 megacycles and asingle, relatively short, non-driven dipole arranged in closely spacedparallel relationship therewith, means for mounting said dipoles withthe long spans of the folded dipole disposed vertically one above theother and with the non-driven dipole disposed substantially centrallybetween the folded dipole and the source of a signal to be received, thefolded dipole being formed of conductor material having an L/D ratio ofat least 80, the non-driven dipole having a length selected to render itresonant as a half-wave element at approximately three times said firstfrequency, and the folded and non-driven dipoles being in such closeproximity, within the range from about 1% to about 5% of a half-wavelength at said first frequency, that their coextensive portions comprisea resonant transmission line section, whereby radiation from one issubstantially counteracted by radiation from the other at about threetimes said first frequency.

References Cited in the file of this patent or the original patent2,380,519 Green July 31, 1945 2,474,480 Keane June 28, 1949 2,485,138Carter Oct. 18, 1949 2,534,592 Goumas Dec. 19, 1950 2,572,166 LorussoOct. 23, 1951 2,580,798 Kolster Jan. 1, 1952 2,700,105 Winegard Ian. 18,1955

